The subject matter described herein relates generally to an improved air separation system for combustible liquids, petroleum-based and renewable and alternative fuels, especially fuel for diesel and other internal combustion engines.
Combustible fuel and especially diesel, engines typically utilize a fuel injection system to timely inject fuel directly into the cylinder. The injection timing is predetermined by the engine designer, and is based on known facts. Any uncontrolled or outside event or condition that affects the injection timing that is not predetermined or that affects the spray pattern, will cause the engine's efficiency to degrade.
A persistent concern for such engines is the presence of air and vapor within the fuel. Entrained air and vapor in combustible fuel and combustible fuel systems, varies with fuel temperature, barometric pressure and altitude of engine operation, filter plugging, and at the different operating RPM's of the engine. Air and vapor present in combustible, especially diesel, fuel, and especially in varying amounts, are not found to be among the predetermined conditions factored into the injection timing parameters. Among the problems presented by their presence is the degradation of engine efficiency due to the compressibility of air/vapor. In unit injectors, this leads to retarded injection timing, spray pattern disruption and a poor burn, in turn, resulting in reduced power output of the engine, increased fuel consumption and increased exhaust emissions. In “Common Rail” systems, the air/vapor displaces the fuel in the “High Pressure Pump” barrel. This prevents the “High Pressure Pump” from reaching its designed output volume. This in turn prevents the system from maintaining the correct pressure for proper spray patterns and injection rates, degrading engine efficiency.
Air also causes permanent damage to the components of the fuel injection system. Air can displace the fuel or lubricant between the barrel and plunger. This allows metal on metal contact and galling of the components, leading to injector failure. Also, as the plunger begins its injection stroke, the sudden compression causes the air bubble to implode. When the collapsing bubble is adjacent to the barrel wall, the outer wall of fuel of the collapsing bubble impacts the barrel surface with sufficient destructive force to dislodge microscopic particles of metal. This is commonly referred to as “pitting of the barrel”, and in time can render the injector useless. “Tip erosion” occurs as the air bubble exits the injector tip. Air, being less viscous than diesel fuel passes through the injector tip more quickly than the fuel. The fuel behind the air bubble suddenly impacts the tip with a force that dislodges microscopic particles of metal. As tip erosion increases the bore size of the ports of the injector tip, a poor spray pattern increasingly results. A decrease of the metal between the ports leads to degradation of the structural integrity of the injector tip, which can eventually lead to the loss of the injector tip and catastrophic engine failure.
The operational deficiencies and inefficiencies of the diesel engine are well known, but commercial implementations of such engines have failed to address this problem.
Applicant has previously provided unique systems and apparatus for removing entrained air from the fuel prior to the fuel's entering into the engine's fuel pump while additionally maintaining a net positive pressure head to the pump inlet, thus reducing pump cavitation and the formation of vapor.
Applicant's U.S. Pat. No. 5,355,860 discloses a three filter system for removing entrained air from diesel fuel. The device, which feeds fuel to the engine's transfer or fuel pump, was an early pioneer approach for removing entrained air from the fuel.
Applicant's U.S. Pat. No. 5,746,184 (the “'184 Patent”), a continuation in part of U.S. Pat. No. 5,355,860, discloses a commercial model of the system that efficiently removes the entrained air and addresses pump cavitation. A product incorporating the principals of the '184 Patent has been successfully sold under the trademark, Fuel Preporator®, model numbers FPI and FP1200 by PureFlow Technologies, Inc. This device utilizes a filter to separate entrained air and vapors from the fuel (Ref. Cummins Service Topic 5-135, 1965) and a “Primary” air/vapor discharge port located on the dirty side of the filter to facilitate the removal of the separated air/vapors. Additionally, a second air/vapor discharge port located on the clean side of the filter is used to discharge air/vapors that have been pressure flashed through the filter. The method of air/vapor separation utilized within or on the clean side of the filter media is passive and depends upon flotation of the bubbles to rise to the discharge port.
Applicant's U.S. Pat. No. 6,729,310 (the “'310 Patent”), brought about a more advanced air/vapor separation system that allowed the device to be substantially reduced in size and to separate air/vapor at much higher fuel flows than earlier models. The first systems, applying the principles of the '310 Patent, were commercially sold as model numbers FP135, FP135A. Much smaller models came about later and were sold under the trademarks AirDog® 80, 100, 150 and AirDog®II 125, 150, 165, and 200 by PureFlow Technologies, Inc.
U.S. Pat. Nos. 6,892,710 and 7,025,048 are patents pertaining to the FASS fuel air separation system manufactured by DPPI, INC. This system utilizes only the secondary or passive air separation method and discharge port 428 as shown in U.S. Pat. No. 5,746,184 prior art patent. And as the U.S. Pat. No. 5,746,184 prior art patent Abstract explains, “As the bubbles are trapped on the (filter) element, they float upwardly for discharge through discharge port (294) (FIG. 8). Bubbles passing through element 94 are swept upwardly for discharge through the outlet side discharge port (428)”.
Although the previous devices provided by Applicant have successfully addressed the issue of removing entrained air from fuel and substantially reduced vapors formed through pump cavitation, additional vapors can form after the transfer pump. These vapors may form within the high pressure bypass valve (pressure relief valve) and fuel lines due to pressure drops and high fuel temperatures.
The Clausius-Clapeyron Equation (see FIG. 1) explains the relationship between pressures and temperatures within a closed loop system and the enthalpy of vaporization of a liquid from plots of the natural log of its vapor pressure versus temperature. This allows one to understand that vapors will form within the fuel system itself. While such vapor formation cannot be prevented, the vapors may be substantially removed before they enter the fuel injection system of the engine.
Applicant herein provides an improved, highly efficient and more cost effective device for separating and virtually eliminating such air and vapor from combustible, especially petroleum-based liquids, adapted for high pressure and other fuel systems. The device has improved air discharge means that enhances the collection and removal of unwanted entrained air and vapors without a significant loss of pressure or flow to the engine. Additionally, in preferred embodiments, the device is to be mounted, e.g., fluidically, after the engine's fuel, e.g., fuel transfer pump, thus eliminating the requirement of an additional pump on the device, and before the fuel enters the fuel injection system of the engine, which would remove any additional vapors formed within or after the engine fuel pump.